1. Field of the Invention
The present invention relates to an optical system for visualizing an object in a light scattering medium. More particularly, the present invention relates to an optical system for visualizing and capturing a blood vessel in a tissue of a living body. The term xe2x80x9clight scattering mediumxe2x80x9d as used herein includes also a light scattering and absorbing medium.
2. Description of the Related Arts
So far, there have been various attempts to visualize or image an object in a light scattering or absorbing medium (see, for example, xe2x80x9cMicroscope Imaging Through Highly Scattering Mediaxe2x80x9d, G. E. Anderson et al., OPTICS LETTERS, Vol. 19, No. 13 published on Jul. 1, 1994).
However, the conventional optical system utilizes a method of suppressing the influence of scattering by increasing the depth of focus in the optical system, so that the resolution is liable to decrease.
The present invention has been made in view of these circumstances and the purpose thereof is to provide an optical system capable of visualizing an object in a light scattering medium, without decreasing the resolution, by imaging with only a light beam emanated at a specific angle from the object in the light scattering medium.
The present invention provides an optical system for visualizing an object comprising an object lens, an imaging lens disposed on an optical axis of the object lens, and a spatial filter disposed on the optical axis between the object lens and the imaging lens, the spatial filter including a first portion away from the optical axis and a second portion adjacent to the optical axis, the first portion being higher than the second portion in light transmittance.